Structure for installing mirror base on glass plate and method for installing mirror base on glass plate

ABSTRACT

This invention relates to a mirror base-installing structure for installing a mirror base on the surface of a glass plate, characterized in that said mirror base is bonded to the surface of said glass plate with a film-like or sheet-like heat-curable adhesive interposed between the mirror base and the glass plate, said adhesive having elasticity or plasticity after heat-cured, and a method for installing the same. The mirror base can be bonded simultaneously with the preparation of a bilayer glass, thereby simplifying the working process.

TECHNICAL FIELD

This invention relates to a structure for installing a mirror base on aglass plate, particularly a mirror base-installing structure suitablefor installing an inner mirror on a front window-shield glass of anautomobile in the inside of the automobile, and a method for installinga mirror base on a glass plate.

BACKGROUND ART

As shown in FIG. 7, an inner mirror such as a room mirror, back mirroror the like is installed at the upper position in front of a driver inthe inside of an automobile occasionally by using a method whereby amirror base 41 is installed on the inner side surface 44 of a frontwind-shield glass 43 with an adhesive 42 and an inner mirror 45 isattached to the mirror base 41. It is known to use a paste-like siliconerubber adhesive or a polyurethane rubber adhesive having a fluidity andalso having excellent heat-resistance, durability and weather-resistanceor a thermoplastic polyvinyl butyral film for bonding an inner mirrorbase of an automobile to the surface of a front wind-shield glass.Particularly, the thermoplastic polyvinyl butyral film is widely used inEuropean and American countries since it can be easily and convenientlybonded simultaneously with the preparation of a bilayer glass.

However, the polyvinyl butyral film has a disadvantage that it has aproperty of easily absorbing moisture, and its adhesive force lowerssubstantially upon absorption of moistures, whereby the attached innermirror is likely to fall off naturally by a shock or the like duringdriving. For this reason, a dealer must take the trouble to alwaysprepare an adhesive for an accidental falling off. Furthermore, thepolyvinyl butyral film has another disadvantage that it becomes too softto retain its adhesive force because of the thermoplasticity, therebythe inner mirror naturally falling off when the temperature of awind-shield rises to a temperature from 60° C. to 80° C.

Moreover, the paste-like adhesive such as polyurethane or siliconerubber has an unsatisfactory external appearance, and also has a problemthat a bonding operation including a finish work during the bonding stepand a finish work after curing the adhesive, is complex since a mirrorbase is installed on a window-shield by coating the adhesive on a mirrorbase and then attaching the adhesive-coated mirror base to thewindow-shield. Particularly, in the case of the polyurethane typeadhesive having a poor UV ray-shielding property, a bonding step is morecomplicated since a mirror base is installed on a glass plate by coatinga black type ceramic color frit on the glass plate, baking the coatingand then bonding the mirror base to the glass plate through the bakedblack type ceramic color frit layer interposed therebetween to shield UVray of the sun's rays. Furthermore, in the case of using thepolyurethane adhesive different from the case of using the polyvinylbutyral film, it is impossible to bond the mirror base simultaneouslywith the preparation of a bilayer glass, and there is a fear that itsmanufacturing cost is increased since an independent manufacturing stepand equipment are required.

An object of this invention is to provide a structure for installing amirror base on a glass plate and a method of installing the mirror baseon the glass plate, which do not have the above-mentioned disadvantagesof the prior art.

DISCLOSURE OF THE INVENTION

This invention provides a mirror base-installing structure forinstalling a mirror base on a glass plate, characterized in that saidmirror base is bonded to said glass plate with a film-like or sheet-likeheat-curable adhesive interposed between the mirror base and the glassplate, said adhesive having elasticity or plasticity after heat-cured,and a method for installing a mirror base on a glass plate,characterized by interposing a film-like or sheet-like heat-curableadhesive, which provides elasticity or plasticity after heat-cured,between said glass plate and said mirror base to be bonded, andcompleting the bonding in an autoclave.

A preferable film-like or sheet like adhesive used in this invention iscross-linkable at a temperature from 50° C. to 200° C. within from 5 to60 minutes, said adhesive having the following physical properties aftercross-linked:

Hardness (JIS-A): from 30 to 90,

Modulus at the elongation of 50% tensed by dumbbell (ASTMD-1822): from 5to 50 kg/cm²,

Breaking strength: from 30 to 400 kg/cm², and

Breaking elongation: from 100 to 1,000%.

Further, the film-like or sheet-like adhesive preferably has thefollowing physical properties in the atmosphere of 20° C.:

Tensile strength by dumbell No. 3 (JIS K6301): from 80 to 120 kg/cm²,

Breaking elongation: from 250 to 600%,

Shore hardness: from 50 to 90 kg/cm², and

Shear strength: from 40 to 90 kg/cm².

Still further, a preferable film-like or sheet-like adhesive used in thepresent invention is an adhesive prepared by molding a silicone rubbercomposition into a film-like or sheet-like shape, particularly anadhesive prepared by molding the following silicone rubber compositioninto a film-like or sheet-like shape, said silicone rubber compositioncomprising:

(A) organopolysiloxane having at least two alkenyl groups bonded tosilicon atoms per molecule

100 parts by weight,

(B) organohydrogen-polysiloxane having at least two hydrogen atomsbonded to silicon atoms per molecule:

an amount so as to provide a molar ratio of hydrogen atom bonded tosilicon atom in this Component (B)/alkenyl group in said Component (A)in the range of from 0.5/1 to 5/1,

(C) wet process type hydrophobic reinforcing silica having a specificsurface area of at least 200 m² /g, which comprises SiO₂ unit andorganosiloxane unit selected from the group consisting of R₃ SiO_(1/2)unit, R₂ SiO unit, RSiO_(3/2) unit and a mixture thereof (wherein each Ris a substituted or non-substituted monovalent hydrocarbonyl group),provided that a molar ratio of organosiloxane unit/SiO₂ unit is from0.08 to 2.0:

from 30 to 150 parts by weight,

(D) acryl-functional silane coupling agent or methacryl-functionalsilane coupling agent:

from 0.05 to 10 parts by weight,

(E) epoxy-functional silane coupling agent:

from 0.05 to 10 parts by weight,

(F) partially allyl etherified polyhydric alcohol:

from 0 to 5 parts by weight,

(G) platinum type compound catalyst:

an amount effective to cure the silicone rubber composition.

As mentioned above, the silicone rubber composition prepared by blendingthe specific wet process type silica and the specific compounds has sucha satisfactory tensile strength that it can be made film-like orsheet-like, and has also an excellent adhesive property.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 6 are vertical sectional views illustrating the main part ofa structure for installing an inner mirror by bonding a mirror base inaccordance with this invention as one embodiment;

FIG. 2 is a vertical sectional view illustrating a modified Example ofthe embodiment as illustrated in FIG. 1;

FIG. 3 is an explanation diagram illustrating a method for a bendingstrength test;

FIG. 4 is an explanation diagram illustrating a method for a shear test;

FIG. 5 is a perspective view illustrating the installed surface of amirror base; and

FIG. 7 is a sectional view illustrating the main part of theconventional mirror base-installing structure.

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 1 and 2 illustrate a structure example wherein a mirror base 4 isbonded to a glass plate 2 such as a wind-shield comprising a laminatedglass 1 in an autoclave by interposing a film-like or sheet-likeadhesive 3 between the mirror base 4 and the glass plate surface 2, andan inner mirror 5 is fixed on the mirror base 4 thus bonded, saidadhesive in the form of film or sheet being heat-curable and providingelasticity or plasticity after heat-cured. Particularly, FIG. 1 is avertical sectional view illustrating an embodiment wherein a mirror base4 is directly bonded to the surface of a glass plate 2 such as awind-shield through a film-like or sheet-like adhesive 3 and an innermirror 5 is installed on said mirror base 4 through an installing part8, said inner mirror 5 having a supporting arm 6, one end of which has amirror 7 and the other end of which is supported on the installing part8 in such a manner as to be freely movable.

Further, FIG. 2 is a vertical sectional view illustrating a modifiedExample of the embodiment as illustrated in FIG. 1, wherein a mirrorbase 4 is bonded with a glass plate 2 such as a wind-shield in such amanner as to be invisible from the outside of an automobile by forming aceramic frit baking layer 9 colored with an opaque color such as blackon the glass plate 2 and then bonding the mirror base 4 to the coloredceramic frit baking layer 9 with a film-like or sheet-like adhesive 3interposed therebetween.

The film like or sheet-like adhesive 3 used in the present invention iscross-linkable at a temperature from 50° C. to 200° C. within from 5minutes to 60 minutes, and the adhesive 3 after cross linked preferablyhas the following physical properties:

Hardness (JIS-A): from 30 to 90,

Modulus at the elongation of 50% tensed by dumbbell (ASTMD-1822): from 5to 50 kg/cm²,

Breaking strength: from 30 to 400 kg/cm², and

Breaking elongation: from 100 to 1,000%

Concrete Examples of the adhesive preferably used, include thermo-crosslinkable type ethylene-vinyl acetate copolymer resin (hereinafterreferred to as "EVA"), thermosetting type, i.e. thermo-cross linkabletype silicone rubber, thermo-cross linkable type ionomer resin,polyamide resin and the like. Particularly, it is preferable to use afilm-like or sheet-like adhesive prepared by molding thermo-crosslinkable type ethylene-vinyl acetate copolymer resin or thermosettingsilicone rubber composition having excellent moisture-resistance,heat-resistance and thermostability.

Among them, particularly preferable silicone rubber composition moldedinto a film-like or sheet-like shape comprises the following components(A) to (G).

COMPOSITION OF SILICONE RUBBER COMPOSITION

(A) organopolysiloxane having at least two alkenyl groups bonded tosilicon atoms per molecule

100 parts by weight,

(B) organohydrogen-polysiloxane having at least two hydrogen atomsbonded to silicon atoms per molecule:

an amount so as to provide a molar ratio of hydrogen atom bonded tosilicon atom in this Component (B)/alkenyl group in said Component (A)in the range of from 0.5/1 to 5/1,

(C) wet process type hydrophobic reinforcing silica having a specificsurface area of at least 200 m² /g, which comprises SiO₂ unit andorganosiloxane unit selected from the group consisting of R₃ SiO_(1/2)unit, R₂ SiO unit, RSiO_(3/2) unit and a mixture thereof (wherein each Ris a substituted or non-substituted monovalent hydrocarbonyl group),provided that a molar ratio of organosiloxane unit/SiO₂ unit is from0.08 to 2.0:

from 30 to 150 parts by weight,

(D) acryl-functional silane coupling agent or methacryl-functionalsilane coupling agent:

from 0.05 to 10 parts by weight,

(E) epoxy-functional silane coupling agent:

from 0.05 to 10 parts by weight,

(F) partially allyl etherified polyhydric alcohol:

from 0 to 5 parts by weight,

(G) platinum type compound catalyst:

an amount effective to cure the silicone rubber composition.

In the composition of the above-mentioned sheet-like silicone rubberadhesive convenient for bonding an inner mirror base, the component (A),i.e. organopolysiloxane is the main component, and preferably has aviscosity of not higher than 1,000,000 centipoise at 25° C. so as to beeasily mixed with the other components and to provide desirable adhesiveproperties. The component (B), i.e. organohydrogen-polysiloxane works asa cross-linking agent for the silicone rubber adhesive composition tocure the composition by reacting with the component (A).

The molar ratio of hydrogen atom bonded to silicon atom in the component(B)/alkenyl group in the component (A) is preferably in the range offrom 0.5/1 to 5/1. If the molar ratio is less than 0.5/1, the curing bycross-linking is not sufficient, while if the molar ratio is higher than5/1, the cured product becomes too hard. Thus, a preferable amount addedis such an amount as to provide the molar ratio of from 0.8/1 to 3/1.

The component (C), i.e. wet type hydrophobic reinfocing silica, providesa molar ratio of organosiloxane unit/SiO₂ unit in the range of from 0.08to 2.0, preferably from 0.08 to 1.5. If the molar ratio is less than0.08, the adhesive properties are lowered and the preservation stabilityis also lowered. On the other hand, if the molar ratio exceeds 2.0, thereinforcing property is remarkably lowered. This silica should desirablyhave a specific surface area of at least 200 m² /g, preferably at least300 m² /g. The silica is added in an amount in the range of from 30 to150 parts by weight, preferably from 40 to 100 parts by weight per 100parts by weight of the component (A). The components (D), (E) and (F)provide an adhesive property, and the component (D) is added in anamount from 0.05 to 10 parts by weight, preferably from 0.1 to 3 partsby weight per 100 parts by weight of the component (A). The component(F) is added in an amount from 0 to 1.5 parts by weight, preferably 0.01to 2 parts by weight per 100 parts by weight of the component (A). Thecomponent (G), i.e. a platinum type compound catalyst, is a catalyst forcuring said silicone rubber adhesive, and is added preferably in anamount from 0.1 ppm to 100 ppm to the component (A).

In the above-mentioned silicone rubber composition, the component (A) isreacted with the component (B) by addition reaction to cure, and thecomponent (B) works as a cross-linking agent for the composition. Thecomponent (C) is a reinforcing agent, and works to maintain thethickness of a molded body to be easily handled before curing and toprovide an appropriate hardness after curing. The components (D), (E)and (F) are indispensable components for providing an adhesive propertywith a metal as a base material in the claim. The component (D), is themain component for enhancing an adhesive strength, but the adhesivestrength is remarkably improved by using the components (E) and (F) incombination.

A film-like or sheet-like molded silicone rubber composition should havea tensile strength at 25° C. during being uncured in the range from 1.5kg/cm² to 5.0 kg/cm² (by dumbbell No. 3 in accordance with JIS K6301),preferably 2.0 kg/cm² to 4.0 kg/cm². If the tensile strength is nothigher than 1.5 kg/cm², it becomes hard to handle the compositionbecause it easily deforms. On the contrary, if the tensile strength isnot lower than 5.0 kg/cm², the composition becomes too hard duringpreservation, thus losing its plasticity.

After curing an adhesive composition to such an extent as to becomesuitable for bonding an inner mirror base, the adhesive compositionshould desirably have physical properties such as a tensile strength bydumbbell No.3 of 60 to 140 kg/cm², a breaking elongation of 250 to 600%and a hardness of 50 to 90 degree (Shore hardness A), preferably atensile strength of 80 to 120 kg/cm², a breaking elongation of 350 to500% and a Shore hardness A of 60 to 80 degree.

A shear strength of an adhesive composition measured by a shear testmethod wherein a test sample prepared by bonding a glass plate 21 to ametal plate 22 with the film-like or sheet-like adhesive composition isdrawn downwardly, as shown in FIG. 4, is in the range from 40 to 90kg/cm², preferably from 50 to 80 kg/cm².

The silicone rubber adhesive film or sheet of the present inventionsuitable for bonding an inner mirror base, preferably has a thickness inthe range from 0.4 mm to 1.5 mm, more preferably from 0.6 to 1.0 mm. Ifthe thickness of the adhesive film or sheet is not more than 0.4 mm, theadhesive composition can not absorb an internal stress generated bythermal expansion difference between the glass plate and the innermirror base metal, thus leading to the breakage of the adhesivecomposition. On the contrary, if the thickness of the adhesive film orsheet is not less than 1.5 mm, the mirror installed thereby tremblesduring driving due to the elasticity of the adhesive composition, thusleading to poor backward visibility.

Examples of the base material for the mirror base 4 include iron,stainless steel (SUS304, SUS430), nickel-plated iron, ironbaking-finished with thermosetting varnish such as thermosettingurethane varnish or the like, zinc-plated iron, die-cast zinc, die-castzinc plated with nickel, die-cast zinc plated with a thermosettingvarnish such as thermosetting urethane varnish or the like, polysulfoneresin (PPS), FRP, nylon resin and the like.

When a flat plate-like mirror base is installed on the concave surfaceof a curved front glass of an automobile with a film-like or sheet-likeadhesive, air remains in the central part of the adhered surface,thereby lowering the adhesive force and degrading the externalappearance since the air bubbles are visible from the outside throughthe glass. In order to solve these problems, it is effective to providethe mirror base with such a convex bonding surface as to be fitted andbonded to the concave side surface of the glass plate by interposing afilm-like or sheet-like adhesive between the convex bonding surface andthe concave side surface of the glass plate.

FIG. 5 illustrates a mirror base 12 having such a convex bonding surface13 as to be fitted to the concave side surface of a curved front glassplate.

FIG. 6 is a vertical section view illustrating one embodiment of amirror base-installing structure wherein the mirror base 12 is installedon the concave side surface 11 of a front glass 10 at the upper positionof the inside of an automobile, said front glass 10 being composed of abilayer glass prepared by bonding two sheets of curved glass plates withan intermediate film. The bonding between the bonding surface 13 and theconcave side surface 11 of the front glass 10 is effected by a film-likeadhesive 15 having a thickness of 0.6 mm, which comprises a thermo-crosslinkable type silicone rubber. The mirror base may be press-molded toform such a convex bonding surface as to be fitted to the curved shapeof the front glass 11, or may be subjected to die-casting usingdie-casting zinc, sintered alloy or the like to provide such a convexbonding surface 13 as to be fitted to the curved shape of the frontglass 11, or may be subjected to abrasive agent-processing, abrasiveprocessing or the like to provide the convex surface shape.

When the mirror base having the above-mentioned shape is bonded to theconcave side surface of the curved glass plate with a film-like orsheet-like adhesive, the bonding surface of the mirror base isintimately bonded to the concave side surface of the glass plate throughthe film-like or sheet-like adhesive without generating air bubbles inthe bonding part since the bonding surface of the mirror base has such aconvex shape as to be fitted to the concave side surface of the curvedglass plate, thus preventing the adhesive force and external appearancefrom degrading due to the presence of the air bubbles.

The following experimental examples illustrate the difference in theeffect on the bonding state of the mirror bases in accordance with thepresent invention and the prior art. Table 1 shows physical propertiesof cross-linked adhesives used in the above experiments.

                  TABLE 1                                                         ______________________________________                                        Physical properties of adhesive                                               Physical property values   Silicone                                           of adhesive      EVA       rubber   PVB                                       ______________________________________                                        Hardness (JIS-A)  65        60       67                                       50% Modulus (kg/cm.sup.2)                                                                       30        20       25                                       Tensile strength (kg/cm.sup.2)                                                                 200       220      190                                       Elongation (%)   500       770      475                                       ______________________________________                                    

A stainless steel (SUS430) sample having a size of 40 ×40 mm was used asa mirror base.

EXAMPLE 1

A laminate prepared by placing an EVA film on the central part of aglass plate of 100×100 mm (5 mm thickness) and further placing a mirrorbase thereon was placed in an autoclave (condition: temperature 150° C.,pressure 13 kg/cm²) to firmly bond each other.

EXAMPLE 2

A laminate prepared by placing a silicone rubber film on the centralpart of a glass plate of 100×100 mm (5 mm thickness) and further placinga mirror base thereon was placed in an autoclave (condition: temperature130° C., pressure 13 kg/cm²) to firmly bond each other.

COMPARATIVE EXAMPLE 1

A laminate prepared by placing a PVB film on the central part of a glassplate of 100×100 mm (5 mm thickness) and further placing a mirror basethereon was placed in an autoclave (condition: temperature 130° C.,pressure 13 kg/cm²) to firmly bond each other.

Each laminate sample thus prepared under the above-mentioned conditionwas subjected to various aging tests as shown in the left column ofTable 2.

After the aging test, each laminate sample was subjected to a breakingstrength test as shown in FIG. 3, wherein the glass plate 31 having themirror base 33 bonded therewith by the adhesive 32 was supported by aglass plate supporting frame 34 and the mirror base 33 is firmlyattached with a supporting rod 35, a pushing pressure of 50 mm/min beingapplied to the supporting rod 35 at the position of 70 mm horizontallyapart from the surface of the glass plate 31. The test results are shownin the right column of Table 2.

                  TABLE 2                                                         ______________________________________                                        Aging test method and breaking strength                                                          Adhesives and                                                                 breaking strength (kg)                                     Test Items                                                                              Test conditions                                                                              Ex. 1   Ex. 2 Ex. 3                                  ______________________________________                                        Initial   at normal      87.5    60.0  83.1                                   strength  temperature of 22° C.                                                  at hot temperature                                                                           80.0    59.0  10.5                                             of 80° C.                                                    Moisture- Exposed at 50° C., RH                                                                 52.3    61.0  20.7                                   resistance                                                                              of 95% for 30 days                                                  Accelerated                                                                             Exposed sunshine                                                                             90.0    67.8  77.5                                   durability                                                                              type weather-ometer                                                           for 1,000 hours                                                     ______________________________________                                    

As can be seen from the test results in Table 2, the breaking strengthof the test sample of the Comparative Example prepared in accordancewith the conventional method was remarkably lowered after hightemperature and moisture-resistance aging test. On the other hand, itwas confirmed that each test sample of Examples 1 and 2 of the presentinvention had excellent heat-resistance and humidity-resistance and itsbreaking strength was not largely lowered.

EXAMPLE 3

A film having a thickness of 0.6 mm molded from a composition comprising(A) Component: dimethylsiloxane-methylvinylsiloxane copolymer 60 wt %,(B) Component: methyl hydrogensiloxane-dimethylsiloxane copolymer 2 wt%, (C) Component: hydrophobic reinforcing silica 38.5 wt % (D)Component: γ-methacryloxypropyltrimethoxysilane 0.5 wt %, (E) Component:γ-glycidoxypropyltrimethoxysilane 0.5 wt %, (F) Component:glycerinmonoallylether 0.4 wt % and chloroplatinic acid 0.1 wt %, wasattached to a stainless steel (SUS 430) base (20×30 mm). Afterlaminating step of interposing an intermediate film between two sheetsof glass plates, the above prepared base attached with the silicone filmwas press-bonded to the bilayer glass at the predetermined part by hand.Thereafter, this laminate product was sealed in a rubber bag which wasevacuated to 500 mmHg, and it was allowed to stand in the atmosphere of90° C. under this circumstances for 10 minutes to be preliminarilypress-bonded. Predetermined sheets of the laminate products thusobtained were vertically placed on a track in an autoclave of theatmosphere of a temperature of 130° C. and a pressure of 13 kg/cm² tofirmly bond the bilayer glass and to cure-bond the silicone film.

EXAMPLE 4

Using the same base and the same silicone film having the samecomposition and the same thickness as in Example 3, the base having thesilicone film attached thereto at 20° C. was press-bonded by hand to thepredetermined part of a bilayer glass laminate product after subjectedto a preliminary press-bonding step. Subsequent steps were the same asin Example 3.

Comparative Examples 2 and 3 were carried out in accordance with thesame steps as in respective Examples 3 and 4, except that comparativesamples were prepared by press-bonding (5 kg load for 5 seconds) thesame base with polyvinyl butyral (PVB) having a thickness of 20 milheated at 100° C.

30 sheets of each sample were prepared by using silicone and PVBrespectively as in Examples 3 and 4, and there was no sample wherein abase fell off from a glass plate till the end of the autoclaveprocessing step. The bilayer glass having the mirror base attachedtherewith as mentioned above was cut into a size of 10 cm×10 cm, and wassubjected to various adhesive durability tests. The test results areshown in the following Table. As can be seen from this Table, thesamples of this invention prepared by using the silicone rubber typesheet-like adhesive have a satisfactory adhesive force and a sufficientdurability.

    __________________________________________________________________________    Examples    Durability test items and breaking strength (kg) *1               and                     Bathed in                                                                             Exposed to                                                                             Exposed to *2                        Comparative 20° C.                                                                       80° C.                                                                       water of 50° C.                                                                atmosphere of                                                                          weather-ometer                       Examples    atmosphere                                                                          atmosphere                                                                          for 30 days                                                                           80° C. for 30 days                                                              test for 2,000                       __________________________________________________________________________                                             hrs                                  Example 3                                                                            Silicone                                                                           65    55    60      67       59                                   Comparative                                                                          PVB  73     5     8      68       75                                   Example 2                                                                     Example 4                                                                            Silicone                                                                           63    56    59      66       67                                   Comparative                                                                          PVB  72     4     6      70       73                                   Example 3                                                                     __________________________________________________________________________     *1 The breaking adhesive strength was measured in accordance with the         method as illustrated in FIG. 4 wherein 31 shows a bilayer glass, 32          showing an adhesive film, 33 showing a mirror base (SUS 430), 34 showing      supporting stand for a bilayer glass, 35 showing a bending load fulcrum       rod and 36 showing a bending cross head (50 mm/min descending speed).         *2 The Weatherometer test was carried out by using a Sunshine                 Weatherometer (Longlife WESUN type) manufactured by Suga Shikenki Ltd.   

According to the present invention, a mirror base can be bondedsimultaneously with the preparation of a bilayer glass, therebysimplifying the working process, and the bonding state of the mirrorbase bonded to the surface of the glass plate is more strengthened thanin the conventional case in respect of heat-resistance,moisture-resistance and durability. Moreover, since the adhesive used istransparent, the mirror base itself can be an appealing point on theexternal view without spoiling the external appearance.

Particularly, when the film-like or the sheet-like adhesive comprisingthe above-mentioned silicone rubber composition is used as an adhesivefor an inner mirror-installing base, it maintains the initial thicknessin the atmosphere of a temperature of 130° C. and a pressure of 13kg/cm² in an autoclave used in the preparation of a bilayer glass.Therefore, the adhesive does not protrude from the periphery of themirror base, thereby providing a merit of omitting a finishing process.

Furthermore, the adhesive is thermosettable, and there is therefore nofear that the adhesive strength is remarkably lowered in the atmosphereof a high temperature like polyvinyl butyral film. Still further, as theadhesive maintains its elasticity even at a low temperature, there is nofear that the mirror falls off by vibrations during driving at a lowtemperature. The adhesive also has a good ultraviolet ray-resistance,and it is therefore unnecessary to protect the bonding face of the glassplate from the ultraviolet ray with a colored ceramic color frit bakinglayer as in the case of using a urethane adhesive.

It was recognized that materials other than SUS 430 could be used as amirror base material, examples of which include metallic materials suchas SUS 340, nickel-plated, zinc die-cast, zinc-plated, bake-finishedsteels or the like, and plastics such as polycarbonate resin,polyacetal, nylon 6, polyphenylene sulfone resin, glass reinforcedpolyester resin or the like.

We claim:
 1. An adhesive composition for installing a mirror base on aglass plate comprising a film or sheet of a cross-linkable siliconerubber composition comprising:(A) an organopolysiloxane having at leasttwo alkenyl groups bonded to silicon atoms per molecule; (B) anorganohydrogenpolysiloxane having at least two hydrogen atoms bonded tosilicon atoms per molecule, in an amount to provide a molar ratio ofhydrogen atoms bonded to silicon atoms in (B)/alkenyl groups bonded tosilicon atoms in (A) in the range of from 0.5/1 to 5/1; (C) wet processhydrophobic reinforcing silica having a specific surface area of atleast 200 m² /g, said silica comprising SiO₂ units and organosiloxaneunits selected from the group consisting of R₃ SiO_(1/2) units, R₂ SiOunits, RSiO_(3/2) units and a mixture thereof, wherein each R is asubstituted or non-substituted monovalent hydrocarbonyl group, saidsilica having a molar ratio of organosiloxane units/SiO₂ units of from0.08 to 2.0, said silica being present in an amount of 30 to 150 partsby weight/100 parts by weight of (A); (D) an acryl-functional silanecoupling agent or a methacryl-functional silane coupling agent, in anamount of from 0.05 to 10 parts by weight/100 parts by weight of (A);(E) an epoxy-functional silane coupling agent, in an amount of from 0.05to 10 parts by weight/100 parts by weight of (A); (F) a partially allyletherified polyhydric alcohol, in an amount of from 0 to 5 parts byweight/100 parts by weight of (A); and (G) a catalytically effectiveamount of a platinum compound catalyst.
 2. The adhesive compositionaccording to claim 1, wherein said organopolysiloxane has a viscosity ofnot higher than 1,000,000 centipoise at 25° C.
 3. The adhesivecomposition according to claim 1, wherein said ratio of hydrogen atomsbonded to silicon atoms in (B)/alkenyl groups bonded to silicon atoms in(A) is in the range of from 0.8/1 to 3/1.
 4. The adhesive compositionaccording to claim 1, wherein said molar ratio of organosiloxaneunits/SiO₂ units is in the range of from 0.08 to 1.5
 5. The adhesivecomposition according to claim 1, wherein said silica has a specificsurface area of at least 300 m² /g.
 6. The adhesive compositionaccording to claim 1, wherein said silica is present in an amount offrom 40 to 100 parts by weight/100 parts by weight of (A).
 7. Theadhesive composition according to claim 1, wherein said acryl-functionalsilane coupling agent or said methacryl-functional silane coupling agentis present in an amount of from 0.1 to 3 parts by weight/100 parts byweight of (A).
 8. The adhesive composition according to claim 1, whereinsaid partially allyl etherified polyhydric alcohol is present in anamount of 0.01 to 2 parts by weight/100 parts by weight of (A).
 9. Theadhesive composition according to claim 1, wherein said catalyst ispresent in an amount of from 0.1 ppm to 100 ppm to (A).
 10. The adhesivecomposition according to claim 1, wherein said film or sheet has athickness in the range from 0.4 mm to 1.5 mm.
 11. The adhesivecomposition according to claim 10, wherein said thickness is in therange from 0.6 mm to 1.0 mm.